Heat a skillet over medium-high heat and add the olive oil. Sear the chicken thighs, skin-side down, until the skin is crispy and golden (about 4–5 minutes). Flip and sear the other side for 2 minutes. This step adds flavor, but you can skip it if you’re short on time; the thighs will still become tender in the slow cooker.
Transfer the seared thighs to the slow cooker. In the same skillet, sauté the onions for 2–3 minutes until translucent, then add the garlic and cook for another 30 seconds until fragrant.
Pour the onion-garlic mixture over the chicken. Add the cubed sweet potatoes, black beans, diced tomatoes with their juices, and chicken broth. Sprinkle paprika, cumin, oregano, red pepper flakes, salt, and pepper over the top.
Cover and cook on low for 6–8 hours or on high for 3–4 hours, until the chicken is tender and the flavors meld together. If your slow cooker runs hot, check at the 5-hour mark on low to avoid overcooking the chicken.
Stir in lime juice right before serving. Taste and adjust seasoning with additional salt, pepper, or chili flakes if you like a bit more heat.
Serve hot, garnished with chopped cilantro if desired. This dish pairs wonderfully with a simple green salad or cornbread to soak up the flavorful sauce.